EP3542052B1 - Wind turbine and method for operating a wind turbine - Google Patents

Description

The present invention relates to a wind power installation. The present invention also relates to a method for parameterizing a wind energy installation and the present invention relates to a method for operating a wind energy installation.

Wind energy installations are known; they generate electrical power from wind, in particular in order to feed them into an electrical supply network. In addition to the advantages of environmentally friendly energy generation, a wind turbine can also be perceived as a nuisance in certain situations. Operating noises from the wind energy installation can be perceived as annoying, particularly when wind energy installations are operated in the vicinity of a populated area.

In particular, wind noise on the rotor blades of the wind energy installation can lead to a more or less loud noise spectrum. In order to reduce such a noise spectrum and thus to make the wind energy installation quieter, it can be proposed in certain situations to reduce the speed of the wind energy installation.

However, other sound sources can also be present. This is because sound can also arise from vibrations in the towers or machine houses of wind turbines, in particular when resonances are excited. Such a sound or the sound produced thereby can also be referred to as structure-borne sound. Increased sound power levels due to this structure-borne noise often occur in narrow frequency bands, are often low-frequency and are perceived as unpleasant by the human ear. In frequency spectra, this structure-borne noise appears as a peak in the respective frequency band.

Such structure-borne noise, in particular the peak mentioned in the frequency spectrum, can also be reduced during operation by throttling the wind energy installation. But it can there is also the effect that a throttled operation of the wind turbine reduces the overall spectrum and thus makes the peak of the structure-borne noise more dominant. This can even have the effect that such structure-borne sound is perceived by the human ear to be even stronger and thus even more unpleasant.

Such structure-borne noise with a pronounced peak in the frequency spectrum is also referred to as tonality.

There are also known methods that save known system resonances in their operation. For this purpose, a speed control is provided in particular, which omits or, if necessary, controls the corresponding rotor speeds as quickly as possible, which stimulate a system resonance. A particular problem with such methods is that a decision has to be made as to whether the system should be operated at a lower or higher speed than the speed range to be omitted. If an otherwise desirable operating point lies in the range of the speed to be omitted, such a decision can be difficult and in the worst case lead to a constant change between the next higher and next lower speed.

The German Patent and Trademark Office researched the following prior art in the priority application for the present application: US 2008/0164091 A1 ; US 2012/0139244 A1 ; WO 2012/139584 A1 and WO 2013/097863 A1 .

The present invention is therefore based on the object of addressing at least one of the problems mentioned. In particular, a solution is to be proposed which reduces the occurrence or perception of such structure-borne noise. At least an alternative solution to previously known solutions is to be proposed.

According to the invention, a wind power installation according to claim 1 is proposed. This has a tower, an aerodynamic rotor and a generator. The aerodynamic rotor, which has several rotor blades, whereby one would also be sufficient in principle, can be operated with a variable rotor speed and the rotor blades are adjustable in their rotor blade angle. The rotor blade angle is generally also referred to as the pitch angle and the adjustment of the rotor blade angle is referred to as the pitch.

To operate the wind energy installation, an operating characteristic is specified which indicates a relationship between the rotor speed and the output power. In particular, the wind energy installation is operated as a function of such an operating characteristic curve in such a way that when the rotor speed sets in, a corresponding output power is set in accordance with the operating characteristic curve. A control system is provided for this purpose, which adjusts the output power in accordance with the operating characteristic as a function of the rotor speed. An operating characteristic with reduced tonality, which can be selected, is now provided as the operating characteristic. It is selected accordingly if the tonality is to be reduced or limited.

This tonality-reduced operating characteristic curve is designed in such a way that an excitation of a system resonance of the wind energy installation is reduced in comparison to an operating characteristic curve with optimum performance. The operating characteristic with reduced tonality is designed in such a way that it does not omit a speed that stimulates system resonance. In particular, this tonality-reduced operating characteristic is a continuous characteristic.

According to the invention, it is therefore proposed to select a different, but not abrupt, operating characteristic in order to reduce or limit the tonality.

It is preferably proposed that the operating characteristic can be selected from the operating characteristic with reduced tonality, the performance-optimized operating characteristic and a noise-reduced operating characteristic. The performance-optimal operating characteristic is the operating characteristic that is designed in such a way that power extraction from the wind is maximized. This performance-optimized operating characteristic can be selected in particular if a sound reduction is not fundamentally necessary, or if no disturbing sound is to be expected in the given situation. This can also depend, for example, on the wind direction if this is such, for example, that the wind only carries sound from the wind energy installation into non-populated areas.

The noise-reduced operating characteristic is designed in such a way that noise emissions from the wind turbine are generally reduced compared to the performance-optimized operating characteristic. In particular, a sound power spectrum of the sound emissions is reduced here. In contrast, the tonality-reduced operating characteristic is deliberately reduced. This can also mean that the overall noise spectrum is not or only slightly reduced compared to the performance-optimized operating characteristic.

Through this selection between the above-mentioned operating characteristics, the wind energy installation can thus easily adjust to the respective circumstances or requirements, while continuous operation or continuous operation is ensured.

According to one embodiment, it is proposed that the tonality-reduced operating characteristic has lower output power values in a resonance speed range than the performance-optimal operating characteristic in the same resonance speed range, the tonality-reduced operating characteristic also being constant in the resonance speed range. The resonance speed range is thus a range in which the rotor speed lies, which excites the system resonance of the wind energy system. Here the tonality-reduced operating curve is at least somewhat flatter than the performance-optimized operating curve.

Both operating characteristics indicate the output power as a function of the rotor speed, whereby an equivalent speed could also be used, and the operating characteristic with reduced tonality is correspondingly lowered here. At least one value of the output power at the resonance speed of the tonality-reduced operating characteristic is smaller than in the performance-optimal operating characteristic. However, the operating characteristic with reduced tonality is also constant in the resonance speed range. It is not a singular value of the output power, but the overall range is smaller, but at least one value of the tonality-reduced operating characteristic is lower than the performance-optimized operating characteristic. In this way, too, the tonality can be taken into account in a targeted manner, in that the power is reduced in a targeted manner in the relevant speed range. In this way, forces acting overall at this speed are also reduced and, accordingly, an excitation of the system resonance is also reduced.

A wind energy installation can in principle also have several installation resonances, but it is assumed here that one installation resonance is dominant and precisely this installation resonance is stimulated less by the proposed measure. At the same time, however, the wind energy installation can be operated with a constant operating characteristic.

The operating characteristic with reduced tonality is preferably also continuously differentiable in the resonance speed range and increases in a strictly monotonous manner. The operating characteristic is thus also after a derivative, i.e. a derivative of the output power according to the rotor speed, continuously. In addition, it increases strictly monotonically, so the output power increases as the rotor speed increases, without there being a falling or constant range. As a result, the operating characteristic can also be used in a simple manner for controlling the wind energy installation for operation with reduced tonality. In particular, it is avoided that undefined and / or unstable areas arise due to horizontal or even falling areas of the operating characteristic for a regulation to be implemented.

According to a further embodiment, it is proposed that the tonality-reduced operating characteristic can be divided into a first, second and third rotor speed range. The first rotor speed range begins at a starting speed, which designates a rotor speed with which the wind energy installation is started. The second rotor speed range has higher speeds than the first rotor speed range and thus follows on from the first rotor speed range. The third rotor speed range has even higher speeds than the second rotor range and reaches up to a nominal speed. The second rotor speed range includes the resonance rotor speed. These three rotor speed ranges and thus also the resonance speed are therefore in a part-load operation or a part-load range. This partial load range thus extends from the beginning of the first rotor speed range to the end of the third rotor speed range. The second rotor speed range is thus a medium range in this partial load range and the resonance speed is located in this medium range. The resonance speed or the resonance speed range is thus the speed or the range at which or in which the system resonance is excited.

For this purpose, it is proposed according to one embodiment that in the second rotor speed range the output power of the tonality-reduced operating characteristic curve is lower than the output power of the performance-optimal operating characteristic curve. It is also proposed that the second rotor speed range in particular include or correspond to the resonance speed range.

According to a preferred embodiment, the wind energy installation is characterized in that a pitch control is provided which sets the rotor blade angle in accordance with a pitch characteristic as a function of the output power generated in partial load operation. Furthermore, the pitch characteristic is dependent on the selected Operating characteristic can be selected from several pitch characteristics. In particular, it is proposed that a separate pitch characteristic be provided for each operating characteristic.

It was recognized here that a variable pitch angle is also useful in partial load operation. Thus, in part-load operation, no predetermined constant optimal angle, that is to say no fixed part-load angle, is used, but rather it is set according to the respective conditions.

Furthermore, it was recognized that depending on the selected operating characteristic, that is to say in particular whether a tone-reduced, noise-reduced or performance-optimized operating characteristic is formed, a corresponding pitch characteristic is selected. The respective pitch characteristic is preferably matched to the respective operating characteristic. The operation of the wind energy installation can thus also be adapted aerodynamically to the respective operating characteristic and thus to the respective operating situation.

It was recognized that by changing the speed-dependent output power, even with the same wind conditions, different rotor speeds and thus high-speed speeds can occur in comparison, for example, with the performance-optimal operating characteristic. Such changes, especially in the high-speed speed, are taken into account by the adapted pitch characteristic.

According to one embodiment, it is proposed that the pitch characteristic can be divided into a first, second and third output power range. The first output power range begins with an output power which corresponds to an output power at which the wind energy installation is started. The second output power range follows this and has correspondingly higher output powers than the first output power range. The third output power range has a higher output power than the second output power range and extends up to a maximum output power of the partial load operation or up to a nominal power of the generator.

In terms of its operating behavior in partial load operation, the wind energy installation is therefore preferably also divided into three output power ranges. This also enables targeted operation, taking into account various situations, even in partial load operation. For this, too, it was recognized that the use of a single constant rotor blade angle in part load operation can in any case be improved for the implementation of the reduction in tonality.

To this end, according to one embodiment, it is also proposed that when selecting the operating characteristic with reduced tonality, an adapted pitch characteristic is specified, which can also be referred to as a pitch characteristic with reduced tonality. Such an adapted pitch characteristic preferably has a larger rotor blade angle in the first output power range than a power-optimal pitch characteristic in the same output power range. A power-optimal pitch characteristic is one that is proposed for use in connection with a power-optimal operating characteristic.

It is therefore proposed that the pitch characteristic can be adapted as a function of the selected operating characteristic. An adapted pitch characteristic is therefore proposed for this. A control of the wind energy installation preferably already contains one or more corresponding pitch characteristics and these can then be selected depending on the selected operating characteristic.

In addition or as an alternative, the adapted pitch characteristic, that is to say the pitch characteristic with reduced tonality, has a larger rotor blade angle in the second output power range than a power-optimal pitch characteristic in the same output power range.

The adapted pitch characteristic is larger in the second output power range, that is to say has a larger rotor blade angle, than a power-optimal pitch characteristic in the same output power range. In addition or as an alternative, the adapted pitch characteristic curve in the second output power range can have a smaller rotor blade angle than compared with the first output power range. The blade angle is accordingly larger in comparison to the power-optimal pitch characteristic and also or alternatively smaller in comparison to the first output power range.

The second output power range preferably corresponds to the second rotor speed range. This means in particular that the wind energy installation is always operated in the second rotor speed range when it is operated in the second output power range. In clear terms, these two areas cover the same wind speed range, but without the wind speed being used for the classification for this is expressly included. The first, second and third output power ranges preferably correspond to the first, second and third rotor speed ranges, respectively. The explanations given above for the individual areas can thus be applied equally to the pitch characteristics and operating characteristics. In particular, a change between the respective first, second and third range can be made both in the case of the pitch characteristic curve and the operating characteristic curve.

According to an alternative, the pitch angle is also set as a function of the rotor speed and pitch characteristics are correspondingly specified as a function of the rotor speed. It is particularly preferably proposed that the same rotor speed ranges be used as a basis for the pitch characteristic as for the operating characteristic.

According to one elimination, it is proposed that the second output power range have a wind speed range of approximately 4 to 10 meters per second. is equivalent to. The second output power range thus relates to a large central range of partial load operation. The advantageous change in the characteristic curves can be used here in particular, the application taking place at a good distance from an initial wind speed and also at a good distance upwards from a transition to full-load operation.

In addition or as an alternative, it is proposed that the second rotor speed range be in a range from approximately 20% to 80% of a nominal speed of the rotor. In this way, too, a large middle range of partial operation is provided for the advantages described for this second rotor speed range. Upper and lower border areas can be left out.

The wind energy installation is preferably characterized in that at least in the second rotor speed range the reduced-tonality operating characteristic has reduced output power values compared to the performance-optimal operating characteristic and that the adapted pitch characteristic has rotor blade angles changed in the same area compared to a performance-optimal pitch characteristic. This at least partially counteracts a deterioration in a performance coefficient that results from a change in the high-speed number. The adjusted pitch characteristic therefore takes this change in the high speed number into account.

In addition, the adapted pitch characteristic can also be changed in the first output power range with respect to the power-optimal pitch characteristic, in which the pitch characteristic has larger blade angles there than the power-optimal pitch characteristic.

By increasing the blade angle, an improvement in aerodynamics can also be achieved.

According to one embodiment, it is proposed that when using the tonality-reduced operating characteristic in the range of wind speeds from a starting wind speed at least up to half the nominal wind speed, the high-speed speed falls strictly monotonically with increasing wind speed. In particular, a slope of less than -2 is proposed. For example, a value of -3 and -4 can also be considered. Values up to -10 are suggested according to one embodiment. This concerns a wind speed normalized to the nominal wind speed.

The ratio of a high-speed number when using the operating characteristic with reduced tonality to a high-speed number when using an operating characteristic with optimum performance is preferably greater than 1. The high-speed number when using the operating characteristic with reduced tone is therefore greater than the corresponding high-speed number when using the operating characteristic with optimum performance.

According to the invention, a method for parameterizing a wind energy installation is also proposed. Here, too, a wind energy installation with a tower and an aerodynamic rotor is used. The aerodynamic rotor can be operated with a variable rotor speed and has several rotor blades each with an adjustable rotor blade angle. In addition, a generator is provided for generating an electrical output power.

For parameterization, a performance-optimal operating characteristic is first determined, which indicates a relationship between the rotor speed and the output power. The performance-optimized operating characteristic curve is selected in such a way that the wind energy installation emits maximum output power as long as it is operated in accordance with this operating characteristic curve.

In addition, a resonance speed is recorded, which describes a rotor speed that excites a system resonance of the wind energy system. Here, too, such a system resonance can be a resonance of the tower, the nacelle or other elements of the wind energy system. A resonance for the wind energy installation as a whole also comes into consideration, in which several elements together determine the installation resonance, such as, for example, the tower and the nacelle together.

Furthermore, an operating characteristic with reduced tonality is determined, which has lower output power values in the resonance speed range compared to the performance-optimal operating characteristic. The operating characteristic with reduced tonality is determined in such a way that it is also constant in the resonance speed range. In fact, an operating characteristic with reduced tonality is determined and not just singular speed power values that are to be specifically controlled or specifically avoided.

The result of this proposed parameterization is, in particular, the determination of the tonality-reduced operating characteristic. Overall, however, at least two operating characteristics are parameterized, namely the performance-optimized and the speed-reduced one. The wind energy installation can then optionally be operated with at least one of these two operating characteristics. If there are no requirements for a reduction in tonality, for example because a suggestion of such tonality is not to be expected anyway or nobody in the vicinity of the wind turbine is disturbed by such tonality, the wind turbine can be operated with the performance-optimized operating characteristic. In this case, a fundamentally known operating characteristic can also be used as the performance-optimal operating characteristic. Only when there is a need to reduce the tonality can this tonality-reduced operating characteristic be used. Preferably, however, the wind energy installation is then operated permanently with the operating characteristic curve which is reduced in tone. In principle, there is no provision for constantly switching back and forth between the performance-optimized operating characteristic and the tonal-reduced operating characteristic.

• die leistungsoptimale Pitchkennlinie,
• die angepasste Pitchkennlinie,
• der erste Rotordrehzahlbereich,
• der zweite Rotordrehzahlbereich,
• der dritte Rotordrehzahlbereich,
• der erste Ausgangsleistungsbereich,
• der zweite Ausgangsleistungsbereich,
• der dritte Ausgangsleistungsbereich und
• die schallreduzierte Betriebskennlinie.

A wind energy installation is preferably parameterized in accordance with at least one of the embodiments described above. At least one element of the following list is parameterized:

• the performance-optimized pitch curve,
• the adjusted pitch curve,
• the first rotor speed range,
• the second rotor speed range,
• the third rotor speed range,
• the first output power range,
• the second output power range,
• the third output power range and
• the noise-reduced operating characteristic.

All these elements have already been described above in connection with embodiments of the wind energy installation and it is proposed to undertake the parameterization precisely in such a way that what emerges is what has been described above in connection with at least one embodiment of the wind energy installation.

According to one embodiment, it is proposed that the detection of the resonance speed take place in such a way that the rotor speed is varied and, for this purpose, a tonality in the vicinity of the wind energy installation is detected. The rotor speed at which the tonality has a maximum is then used as the resonance speed. This is preferably done in a predetermined test frequency range, which is in a range between 10 Hz and 100 Hz.

Tonality is a dominant noise, especially of one frequency. The overall sound power of a sound power spectrum is therefore not recorded, but rather the proportion of such a noise of a frequency is specifically considered. Such a noise of a frequency increases particularly strongly when the rotor speed has a value with which the wind energy installation is excited in such a way that this noise occurs. In particular, this is structure-borne noise that is emitted by this wind energy installation as a result of a corresponding movement of the wind energy installation.

Based on a resonance speed recorded in this way, the operating characteristic with reduced tonality can then also be determined. An adapted pitch characteristic can then be determined based on this. Such an adapted pitch characteristic can also be referred to as a pitch characteristic with reduced tonality because it can be assigned to at least one operating characteristic with reduced tonality.

The tonality-reduced operating characteristic is preferably determined in such a way that the output power in the resonance speed range, in particular at the resonance speed, is reduced compared to the performance-optimal operating characteristic to such an extent that the tonality recorded in the vicinity of the wind turbine falls below a predetermined limit value. The reduction of the output power and the recording of the tonality are preferably repeated or carried out in a continuous process until the value falls below the predetermined limit value.

Here, too, a special noise of a frequency is examined, specifically that which occurs at the resonance speed, especially if the resonance speed was recorded as described above. The system is thus preferably operated at the resonance speed and the power is reduced until this noise at one frequency falls below the predetermined limit value. The operating characteristic with reduced tonality can then be designed in such a way that it has the low value of the generator speed found in this way at this resonance speed. In this case, however, the operating characteristic is specified in such a way that it is continuous, in particular continuously differentiable and strictly increasing in a monotonous manner. The result is then an operating characteristic that has a low power value at the resonance speed. However, this does not mean that overall much less power is generated than in comparison to the power of the power-optimal operating characteristic at the same speed. Rather, a different operating point is established. A strictly monotonously increasing operating characteristic will result in an operating point of higher speed. It should also be noted that operation according to an operating characteristic with reduced tonality, that is to say the reduction in tonality at all, can also mean an increased or at least not reduced sound power spectrum. Operation in which the sound power level is reduced can also mean an increase or at least not a reduction in tonality. For the tonality or the perception of a noise of an isolated frequency, in particular the ratio of such a dominant noise of a frequency in comparison to the rest of the sound power spectrum is important.

According to the invention, a method for operating a wind energy installation is also proposed. Here, too, the wind energy installation has a tower, an aerodynamic rotor and a generator for generating electrical power, as has already been described above in connection with a wind energy installation explained according to the invention.

To operate the wind energy installation, an operating characteristic is specified which indicates a relationship between the rotor speed and the output power and the output power is set according to the operating characteristic as a function of the rotor speed. An operating characteristic with reduced tonality can be selected as the operating characteristic. This is designed in such a way that an excitation of a system resonance of the wind energy system is reduced compared to a performance-optimized operating characteristic, without, however, a rotational speed that stimulates resonance of these systems being omitted. In particular, it is proposed that the wind energy installation be operated in such a way as also emerges from the explanations of the embodiments of wind energy installations according to the invention described above. It is preferably also proposed that a wind energy installation according to an embodiment described above is used.

According to a preferred embodiment, it is proposed that, depending on an external specification or a time of day, a switch is made between operating the wind turbine with the reduced-tonality operating characteristic, and operating the wind turbine with the performance-optimized operating characteristic, which is designed in such a way that power extraction from the wind is maximized , and an operation of the wind energy installation with a noise-reduced operating characteristic which is designed in such a way that the sound emissions of the wind energy installation, in particular a sound power spectrum of the sound emissions, are reduced compared to the performance-optimal operating characteristic. It is thus possible to choose between a performance-optimized operation, a tone-reduced operation and a noise-reduced operation. The choice is made in such a way that a corresponding operating characteristic is selected. Here, too, it should be emphasized once again that operation with reduced tonality, and thus an operating characteristic with reduced tonality, is fundamentally different from noise-reduced operation or a noise-reduced operating characteristic.

In addition, a wind energy installation is very fundamentally proposed which satisfies at least one embodiment of a wind energy installation described above and has been parameterized according to an embodiment describing a parameterization and is also or alternatively described with a method according to a described embodiment.

Figur 1

zeigt eine Windenergieanlage in einer perspektivischen Darstellung.

Figuren 2 und 3

zeigen jeweils ein Diagramm mit unterschiedlichen Betriebskennlinien.

Figuren 4 und 5

zeigen jeweils ein Diagramm mit unterschiedlichen Verläufen von Schnelllaufzahlen.

Figur 6

zeigt ein Diagramm mit Verläufen unterschiedlicher Leistungsbeiwerte.

Figuren 7 und 8

zeigen jeweils ein Diagramm mit unterschiedlichen Pitchkennlinien.

Figur 9

zeigt schematisch ein Diagramm eines Schallleistungspegels.

Figur 10

zeigt schematisch eine Regelungsstruktur zur Umsetzung einer Regelung gemäß einer Ausführungsform der Erfindung.

The invention will now be described in more detail below by way of example on the basis of embodiments with reference to the accompanying figures.

Figure 1

shows a wind turbine in a perspective illustration.

Figures 2 and 3

each show a diagram with different operating characteristics.

Figures 4 and 5

each show a diagram with different courses of high-speed numbers.

Figure 6

shows a diagram with different performance coefficients.

Figures 7 and 8

each show a diagram with different pitch characteristics.

Figure 9

shows schematically a diagram of a sound power level.

Figure 10

shows schematically a control structure for implementing a control according to an embodiment of the invention.

Figure 1 shows a wind energy installation 100 with a tower 102 and a nacelle 104. A rotor 106 with three rotor blades 108 and a spinner 110 is arranged on the nacelle 104. The rotor 106 is set in rotation by the wind during operation and thereby drives a generator in the nacelle 104.

According to the invention, it was recognized that the operation of wind turbines not only generates sound caused by the flow around the rotor blade, but also sound caused by vibrations in the towers or machine houses or other elements, especially in the case of resonances. Increased sound power levels due to this structure-borne noise often occur in narrow frequency bands, are often low-frequency and are perceived as unpleasant by the human ear. In frequency spectra, this structure-borne noise-induced noise appears as a peak in the respective frequency band and is taken into account with a tonality allowance in the sound emission assessment of the wind turbine.

Figure 9 illustrates such a frequency spectrum. There the sound power level L is plotted purely schematically as a diagram as a function of the frequency f. As the sound power level L ₁ , a sound power level is shown schematically with a solid line Line shown. An essentially reduced sound power level L ₂ and an overall increased sound power level L ₃ are also shown schematically for the purpose of explanation.

At the resonance frequency f _{R there} is a peak L _P which shows tonality. It can be seen here that this peak L _P shows itself to be even clearer when the sound power level is reduced overall, as is the case with the reduced sound power level L ₂ . Conversely, the dominance of the peak can decrease _{with the increased sound power level L 3.}

According to the invention, it has now been recognized that the occurrence of resonances and the resulting tonality can be minimized by a clever selection of the operating characteristic, that is, the specification of the electrical output power as a function of the generator speed. In the event that the resonance and the associated tonality are caused by the generator, the tonality can be minimized particularly effectively by adapting the operating characteristic.

Figure 2 shows an example of a change in operating characteristics. Figure 2 shows three different operating characteristics, i.e. the functional relationship between the electrical output power P of the wind turbine and the rotor speed n. In addition to a performance-optimal operating characteristic 200, two tone-reduced characteristics 202 and 204 are shown. This performance-optimal characteristic curve thus describes how the system is operated in the performance-optimal operating mode when there is no tonality of the system or does not have to be reduced, and thus corresponds to a characteristic curve of the prior art.

In the event that tonality occurs in the system and has to be reduced, the two tonality-reduced operating characteristics 202 and 204 are proposed. In the underlying wind turbine, there was an increased sound power level in the form of a peak in a frequency range that was particularly excited at a normalized speed in the range of 0.8. Thus, this normalized speed of 0.8 is here one or the resonance speed.

To avoid this tonality, it is proposed to reduce the power consumption of the generator in this speed range. The two operating characteristics 202 and 204 with reduced tonality can be used for this purpose. With both Operating characteristics 202 and 204 with reduced tonality mean that at the normalized resonance speed of 0.8 the power was reduced by more than 40 percent compared to the optimal operating characteristic. The two operating characteristic curves 202 and 204 with reduced tonality differ structurally. The tonality-reduced operating characteristic curve 204 already provides smaller powers at the beginning than in the case of the performance-optimal characteristic curve, while the other tonality-reduced characteristic curve 202 initially coincides with the performance-optimal characteristic curve 200 at low speeds. In any case, however, both tonality-reduced operating characteristics 202 and 204 are operating characteristics with a continuous profile, which are also steady, continuously differentiable in the resonance speed range and, moreover, are also strictly monotonically increasing. The characteristic curves 202 and 204 with reduced tonality can thus basically be used as a basis very similar to the operational control or system regulation, as the performance-optimal operating characteristic 200.

Figure 3 shows to Figure 2 just another example. In the diagram of the Figure 3 the critical normalized speed range is also around 0.8. Here, too, a performance-optimized operating characteristic 300 is drawn in, as well as three operating characteristic curves with reduced tonality 302, 304 and 306. All operating characteristic curves with reduced tonality 302, 304 and 306 and, moreover, also those of the Figure 2 are examples of operating characteristics with reduced tonality according to the invention.

The three tonality-reduced operating characteristics 302, 304 and 306 also lead to a reduction in power to approximately half compared to the performance-optimal operating characteristic at the normalized resonance speed, which is 0.8 here. According to the invention, however, it was also recognized that the here particularly to the Figures 2 and 3 The procedure described can indeed avoid or reduce a tonality that occurs, but by adapting the operating characteristic, the optimum high-speed number range of the rotor blade is left, namely towards higher high-speed numbers. This is illustrated by two examples in the Figures 4 and 5 explained.

With the proposed operating characteristic curves with reduced tonality, the rotor blades rotate faster than before at the same wind speed, that is to say faster than when using the respectively shown performance-optimal operating characteristic. For this purpose, it was recognized that the axial induction in the rotor blade plane increases, which typically leads to reduced performance coefficients. It was thus recognized that initially, without any further proposed solutions, the Figures 2 and 3 explained avoidance or a reduction in the tonality can lead to a loss of yield of the wind turbine.

Figure 4 and Figure 5 basically show the progression of the high-speed figures to the corresponding operating characteristics of the Figures 2 or 3, if the pitch characteristics are not adjusted. The curves 400, 402 and 404 of the high-speed number λ correspond to the operating characteristics 200, 202 and 204 of FIG Figure 2 . In Figure 4 a characteristic curve with some measuring points is also drawn in and this characteristic curve reproduces measurements and thus confirms the remaining curves that are calculated or simulated. In Figure 5 The high-speed number courses 500, 502, 504 and 506 correspond to the operating characteristics 300, 302, 304 and 306 of FIG Figure 3 . In both Figures 4 and 5 an optimal high-speed number range λ _{OPT is also} shown. It can be seen that the courses of the high-speed numbers which do not belong to the performance-optimal operating characteristic curve, to a large extent, fall out of the optimal high-speed number range. It was thus recognized that the wind turbines are not running optimally in this respect and a remedy is proposed for this.

In the event of Figure 2 is such a loss of the coefficient of performance c _p in Figure 6 shown. The courses of the c _p values 600, 602 and 604 correspond to the operating characteristics 200, 202 and 204 of FIG Figure 2 . The optimal C _P value C _{P_OPT is drawn in and it can be seen that for the tonality-reduced} operating characteristic 604, at least for lower wind speeds V _W , a significantly reduced c _p value is established. The operating characteristic curve 202 with reduced tonality also leads to a worse curve 602 for the c _p value. Incidentally, in Figure 6 a measured value c _M for the c _p value is also shown.

In each case, a significant drop in the performance coefficient up to a wind speed of around 10 meters per second can be observed. In order to partially or even completely compensate for this loss of yield, it is therefore also proposed to modify the pitch characteristic in addition to the operating characteristic. It was thus also recognized that an important aspect is that the change in the operating characteristic also changes the pitch characteristic. The relationship between the electrical output power P _el and the pitch angle of the rotor blades stored in the system control is referred to as the pitch characteristic. The electrical output power is considered to be the power that the system actually delivers and can feed into an electrical supply network. There are various ways of doing this Take this output power into consideration, for example, to determine it from the DC voltage intermediate circuit if a full converter concept with a DC voltage intermediate circuit is used. However, a current-voltage measurement at the output terminals of the wind energy installation can also be considered. The output power can therefore also be referred to synonymously as the system power.

It is therefore now proposed to adapt the pitch characteristic in order to avoid that with the present increase in the high-speed figures during operation with the characteristic according to the invention, yield losses of the wind energy installation are to be expected. It is therefore important for the present invention, at least for one embodiment, to propose a new operating characteristic as well as a new pitch characteristic, namely in particular an operating characteristic with reduced tonality and a pitch characteristic adapted to it, which can also be referred to as a pitch characteristic with reduced tonality.

Figures 7 and 8th each show a pitch characteristic 700 or 800 for an optimal performance operating characteristic 200 or 300 according to FIG Figure 2 respectively. Figure 3 and an adapted pitch characteristic curve 702 or 806, which is assigned to the respective operating characteristic curve 202 or 306 with reduced tonality. A partial load angle α _{T is} drawn in in each case, which designates the blade angle that is used in normal performance-optimal operation as the blade angle in partial load operation.

In the Figure 7 it can be seen that the minimum pitch angle has been increased compared to the partial load angle α _T. As a result, it was possible to compensate for loss of income through the proposed operating characteristic curve with reduced tonality. This is in the Figure 6 It can be seen from the course of the performance coefficient 606 that the performance coefficient could be improved by this measure, that is to say by changing the blade angle 702. This changed course 606 of the power coefficient now differs only slightly from the course 600 of the power coefficient for the performance-optimal operating characteristic.

Figure 8 shows a course 806 of the blade angle or a pitch characteristic, in which or the course of the pitch angle of the performance-optimal operating characteristic was modified in a somewhat more complex form in order to avoid yield losses. The minimum pitch angle is increased up to approx. 6 m / s, in order to then reduce it again to the partial load angle α _T up to approx. 8 m / s.

the Figures 7 and 8th show the profile of the blade angle as a function of the wind speed V _W. For a practical implementation, however, it is suggested to store pitch characteristics. Here the blade angle can particularly depend on a rotor speed and can be adjusted as a function of it. The respective operating point of the wind energy installation can be easily detected via the rotor speed, for example, and a blade angle can be selected accordingly. As a result, a blade angle will be set as a function of the wind speed, namely as in FIG Figures 7 or 8th shown. However, the wind speed is not considered for this, at least not exclusively.

Figure 10 illustrates a possible implementation. Operating characteristics 01, 02 and 03 are stored there and you can switch between them via an external signal ext. The input variable of these operating characteristics O1, 02 and 03 forms the speed n and a power P results as output values. This power P is then to be set for the generator. One possibility is to do this at least partially by changing an excitation current, which is indicated by the block I _E. The result is then an excitation current I _E , which can be input directly to the rotor of the generator Gen, at least when the generator is a separately excited synchronous machine. But there are also other possibilities, such as influencing a stator current of the generator.

In addition, three pitch characteristics P1, P2 and P3 are stored, between which you can also choose. The representation of the Figure 10 is intended to indicate that the same external signal ext is also used for a corresponding selection between the pitch characteristics. The selection should be made in such a way that a pitch characteristic P1, P2 or P3 is assigned to the operating characteristic curve O1, 02 or 03 and thus the operating characteristic O1 with the pitch characteristic P1, the operating characteristic 02 with the pitch characteristic P2 and the operating characteristic 03 is operated or used together with the pitch characteristic curve P3. The operating characteristic curve O1 can stand for a performance-optimal operating characteristic curve and the operating characteristic curve 02 can stand for an operating characteristic curve with reduced tonality. The operating characteristic 03 can, for example, stand for a noise-reduced operating characteristic, or also for an alternative, that is to say further operating characteristic with reduced tonality.

The structure of the Figure 10 shows that the operating characteristics P1, P2 and P3 receive the power P as an input variable. For the sake of simplicity, the power P used, which forms the output of one of the three pitch characteristics P1, P2 and P3. This is intended here to illustrate the use of the output power of the wind energy installation. Instead of the power P, the rotor speed or an equivalent speed can also be used with a correspondingly adapted pitch characteristic, especially when using a gearbox, which is usually better to avoid, however, it ultimately has the same effect, whether the rotor speed of the aerodynamic rotor or a generator speed is used to give just one example. In any case, the output value of the pitch characteristics P1, P2 and P3 is the blade angle a. This can be given to a respective adjusting motor, which is identified here as motor M, which in turn sets the respective blade angle of the rotor blade B.

If necessary, it can be advantageous to provide different dynamics between the power setting of the generator by the respective operating characteristic on the one hand and the adjustment of the blade angle by the corresponding pitch characteristic on the other hand in order to ensure stable behavior. At the in Figure 10 illustrated structure, especially through the use of the actuator I _E to adjust the excitation current, however, the adjustment of the power of the generator should already be significantly faster than the blade adjustment, so that this already gives different dynamics and thus a stability of the control.

Claims (15)

1. A wind power installation (100) with

   - a tower (102),

   - an aerodynamic rotor (106), wherein the aerodynamic rotor (106)

   - can be operated with a variable rotor speed (n) and

   - has a number of rotor blades (108) respectively with an adjustable rotor blade angle (α),

   - a generator (Gen) for generating an electrical output power,

   wherein

   - for operating the wind power installation (100) an operating characteristic (200, 202, 204, 300, 302, 304, 306), which indicates a relationship between the rotor speed (n) and the output power (P), is specified and

   - a controller, which sets the output power (P) in a way corresponding to the operating characteristic (200, 202, 204, 300, 302, 304, 306) in dependence on the rotor speed (n), is provided, wherein

   - selectable as the operating characteristic (200, 202, 204, 300, 302, 304, 306) is a reduced-tonality operating characteristic (202, 204, 302, 304, 306), which is designed such that an excitation of a system resonance of the wind power installation (100) is reduced as compared with an optimum-power operating characteristic (200, 300), without however excluding a speed (2) that excites this system resonance and characterized in that

   - it is provided with a pitch control, which sets the rotor blade angle (α) in dependence on the generated output power in partial-load operation in a way corresponding to a pitch characteristic (700, 702, 800, 806), and wherein the pitch characteristic (700, 702, 800, 806) is adapted in dependence on the selected operating characteristic (200, 202, 204, 300, 302, 304, 306), in particular is selectable from a number of pitch characteristics (700, 702, 800, 806), in particular a dedicated pitch characteristic is provided for each operating characteristic.
2. The wind power installation (100) as claimed in claim 1,
   characterized in that
   the operating characteristic (200, 202, 204, 300, 302, 304, 306) is at least selectable from

   - the reduced-tonality operating characteristic (202, 204, 302, 304, 306),

   - the optimum-power characteristic (200, 300), which is designed such that taking power from the wind is maximized, and

   - the reduced-sound operating characteristic, which is designed such that sound emissions of the wind power installation (100), particularly a sound power range of the power emissions, is/are reduced as compared with the optimum-power operating characteristic (200, 300).
3. The wind power installation (100) as claimed in claim 1 or 2,
   characterized in that

   - the reduced-tonality operating characteristic (202, 204, 302, 304, 306) has lower values of the output power (P) in a resonance speed range of a rotor speed (n) exciting a system resonance of the wind power installation (100) than the optimum-power operating characteristic (200, 300) in the same resonance speed range,

   and wherein the reduced-tonality operating characteristic (202, 204, 302, 304, 306) is also steady in the resonance speed range, wherein in particular even in the resonance speed range, the reduced-tonality operating characteristic (202, 204, 302, 304, 306) is continuously differentiable and strictly monotonously rising.
4. The wind power installation (100) as claimed in one of the preceding claims, characterized in that

   - the reduced-tonality operating characteristic (202, 204, 302, 304, 306) can be divided into a first, second and third rotor speed range and

   - the first rotor speed range begins at a starting speed, which denotes a rotor speed with which the wind power installation (100) is started,

   - the second rotor speed range has higher rotational speeds (n) than the first rotor speed range and

   - the third rotor speed range has higher rotational speeds (n) than the second rotor speed range and extends up to a rated speed, and wherein

   - the second rotor speed range comprises the resonance rotor speed and

   - in the second rotor speed range the output power (P) of the reduced-tonality operating characteristic (202, 204, 302, 304, 306) is lower than the output power (P) of the optimum-power operating characteristic (200, 300), wherein

   - the second rotor speed range in particular comprises the resonance speed range, or corresponds to it.
5. The wind power installation (100) as claimed in one of the preceding claims, characterized in that

   - a or the pitch characteristic (700, 702, 800, 806) can be divided into a first, second and third output power range and

   - the first output power range begins at a generator power (P) which corresponds to an output power (P) with which the wind power installation (100) is started,

   - the second output power range has higher output powers (P) than the first output power range and

   - the third output power range has higher output powers (P) than the second output power range and extends up to a maximum output power (P) of partial-load operation or up to a rated power of the generator (Gen), and wherein

   - when selecting the reduced-tonality operating characteristic (202, 306), an adapted pitch characteristic (702, 806) is specified, and

   - the adapted pitch characteristic (702, 806) has a greater rotor blade angle (α) in the first output power range than an optimum-power pitch characteristic (700, 800) in the same output power range and/or

   - the adapted pitch characteristic (702, 806) has a greater rotor blade angle (α) in the second output power range than an optimum-power pitch characteristic (700, 800) in the same output power range, and/or the adapted pitch characteristic (806) has a smaller rotor blade angle (α) in the second output power range than in the first output power range, wherein in particular

   - at least the second output power range corresponds to the second rotor speed range, and further in in particular

   - the second output power range corresponds to a wind speed range of approximately 4 to 10 m/s and/or

   - the second rotor speed range lies in the range of approximately 20% to 80% of the rated speed of the rotor (106).
6. The wind power installation (100) as claimed in one of the preceding claims,
   characterized in that
   at least in the second rotor speed range, the reduced-tonality operating characteristic (202, 204, 302, 304, 306) has reduced values of the output power (P) as compared with the optimum-power operating characteristic (200, 300) and the adapted pitch characteristic (702, 806) has in the same range changed rotor blade angles (α) as compared with an optimum-power pitch characteristic (700, 800), in order to at least partially counteract a worsening of a power coefficient that occurs due to changing a tip speed ratio (λ), wherein optionally the adapted pitch characteristic (702, 806) is also changed as compared with the optimum-power pitch characteristic (700, 800) in the first output power range, in that it has greater rotor blade angles (α) there than the optimum-power pitch characteristic (700, 800), wherein in particular
   when using the reduced-tonality operating characteristic (202, 204, 302, 304, 306) in the range of wind speeds (V_w) from a starting wind speed at least up to half the rated wind speed, the tip speed ratio (λ) is strictly monotonously descending with increasing wind speed, in particular with a slope of less than -2, in the case of a wind speed normalized to the rated wind speed, in particular of -2 to -10, preferably of -2 to -4.
7. The wind power installation (100) as claimed in one of the preceding claims,
   characterized in that
   the ratio of a tip speed ratio (λ) when using the reduced-tonality operating characteristic (202, 204, 302, 304, 306) to a tip speed ratio (λ) when using an optimum-power operating characteristic (200, 300) is greater than 1.
8. A method for parameterizing a wind power installation (100) with a tower (102) and an aerodynamic rotor (106), wherein the aerodynamic rotor (106) can be operated with a variable rotor speed (n) and has a number of rotor blades (108) respectively with an adjustable rotor blade angle (α), and with a generator (Gen) for generating an electrical output power (P),
   comprising the steps of

   - determining an optimum-power operating characteristic (200, 300), which indicates a relationship between the rotor speed (n) and the output power (P), wherein the optimum-power operating characteristic (200, 300) is chosen such that the wind power installation (100) delivers maximum output power (P) as long as it is operated in a way corresponding to this operating characteristic (200, 300),

   - recording a resonance speed, which describes a rotor speed (n) that excites a system resonance of the wind power installation (100),

   - establishing a resonance speed range around the resonance speed (n),

   - determining a reduced-tonality operating characteristic (202, 204, 302, 304, 306) that has lower values of the output power (P) in the resonance speed range as compared with the optimum-power operating characteristic (200, 300), wherein the reduced-tonality operating characteristic (202, 204, 302, 304, 306) is also steady in the resonance speed range and

   - adapting a pitch characteristic (700, 702, 800, 802) in dependence on the selected operating characteristic (200, 202, 204, 300, 302, 304, 306), wherein a pitch control is provided which sets the rotor blade angle (α) in accordance with a pitch characteristic (700, 702, 800, 806) in dependence on the generated output power in a partial-load operation.
9. The method as claimed in claim 8,
   characterized in that
   a wind power installation (100) as claimed in one of claims 1 to 7 is parameterized, thereby establishing at least one from the list comprising

   - the optimum-power pitch characteristic (700, 800),

   - the first rotor speed range,

   - the second rotor speed range,

   - the third rotor speed range,

   - the first output power range,

   - the second output power range,

   - the third output power range and

   - the reduced-sound operating characteristic.
10. The method as claimed in claim 8 or 9,
    characterized in that
    the recording of the resonance speed takes place by varying the rotor speed (n) and recording a related tonality in the vicinity of the wind power installation (100) and the rotor speed (n) at which the tonality has a maximum is used as the resonance speed, in particular in a predetermined test frequency range, which lies in a range between 10 Hz and 100 Hz.
11. The method as claimed in one of claims 8 to 10,
    characterized in that
    the reduced-tonality operating characteristic (202, 204, 302, 304, 306) is determined such that the output power (P) in the resonance speed range, in particular at the resonance speed, is reduced as compared with the optimum-power operating characteristic (200, 300) to the extent that a or the tonality recorded in the vicinity of the wind power installation (100) goes below a predetermined limit value, in particular in that the process of reducing the output power (P) and recording the tonality is repeated until it goes below the predetermined limit value.
12. A method for operating a wind power installation (100) with a tower (102) and an aerodynamic rotor (106), wherein the aerodynamic rotor (106) can be operated with a variable rotor speed (n) and has a number of rotor blades (108) respectively with an adjustable rotor blade angle (α), and with a generator (Gen) for generating an electrical output power (P), wherein

    - an operating characteristic (200, 202, 204, 300, 302, 304, 306), which indicates a relationship between the rotor speed (n) and the output power (P), is specified for operating the wind power installation (100), and

    - the output power (P) is set in dependence on the rotor speed in a way corresponding to the operating characteristic (200, 202, 204, 300, 302, 304, 306), wherein

    - selectable as the operating characteristic (200, 202, 204, 300, 302, 304, 306) is a reduced-tonality operating characteristic (202, 204, 302, 304, 306), which is designed such that an excitation of a system resonance of the wind power installation (100) is reduced as compared with an optimum-power operating characteristic (200, 300), without however excluding a speed (n) that excites this system resonance and wherein

    - depending on the selected operating characteristic (200, 202, 204, 300, 302, 304, 306), a pitch characteristic (700, 702, 800, 806) is adapted, wherein a pitch control sets the rotor blade angle (α) according to a pitch characteristic (700, 702, 800, 806) in dependence on the generated output power in a partial-load operation.
13. The method as claimed in claim 12,
    characterized in that
    the wind power installation (100) has been parameterized by a method as claimed in one of claims 8 to 12 and/or in that a wind power installation (100) as claimed in one of claims 1 to 11 is used.
14. The method as claimed in claim 12 or 13,
    characterized in that
    in dependence on an external specification or a time of day, switching takes place between,

    - operation of the wind power installation (100) with the reduced-tonality operating characteristic (202, 204, 302, 304, 306),

    - operation of the wind power installation (100) with the optimum-power operating characteristic (200, 300), which is designed such that taking power from the wind is maximized, and

    - operation of the wind power installation (100) with a reduced-sound operating characteristic, which is designed such that sound emissions of the wind power installation (100), particularly a sound power range of the sound emissions, is/are reduced as compared with the optimum-power operating characteristic (200, 300).
15. The wind power installation (100) as claimed in one of claims 1 to 7,
    characterized in that
    it has been parameterized by a method as claimed in one of claims 8 to 11 and/or is operated by a method as claimed in one of claims 12 to 14.

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